meltdown.injapanafterthe bears quake the cooling system failed and the fuel rods got hot and boiled through all of the water and were exposed to the air for hours. to keep the reactor from overheating sea water was pumped into the plant. what a full meltdown occurs the fuel rods melt and turned into more a nonnuclear fuel. it it then sells through the chamber it's considered a meltdown. the major concern here is the containment shell. it the this and hold catastrophic about of radiation can be released into the atmosphere. kate thompson kron 4 news. >>pam: the nuclear crisis in japan has left many people with health questions about radiation exposure and how to protect yourself. christine has when talking with the state health experts, she's here with answers. >>christine: a lot of questions about potassium iodide and how it works. the drug does is it shields of thyroid from radioactive iodine which can cause cancer. think of the thyroid like a gas tank, if you fill up the tank with potassium iodide, the good guy died and that helps provide that it had died from coming in. that's ki